Our long term goal is to understand the functional organization of the cell nucleus and how the processes of transcription, pre-mRNA splicing, and RNA transport are coordinated to allow the cell to function with a high degree of fidelity. Once functional domains are characterize we will have the basis to examine this organization in cells or tissues associated with various disease states with the potential of developing phenotypic screens for susceptibility and/or diagnosis of abnormalities based upon the reorganization of components involved in critical cellular processes. Our short term goals are to determine the rules for the dynamics of pre-mRNA splicing factors in living cells and the functional roles of interchromatin granule clusters (IGCs). In particular, we will: examine whether IGCs occur in predetermined sites, determine if different splicing factors are recruited together or in separate pools, elucidate the turnover rate of splicing factors in IGCs, and determine the effect of dispersion of IGCs on RNA poI. II transcription. We will also determine if the transcription machinery (poI. II CTD) or gene position in the nucleus influences or regulates splicing factor recruitment. Finally, we will biochemically characterize the protein constituents of interchromatin granule clusters (IGCs)l in order to elucidate novel proteins that may play structural/functional roles in these nuclear compartments. These studies have the potential of revealing candidate proteins that will bring us closer to understanding the role(s) of IGCs in nuclear organization have the potential to result in alterations in gene expression, the end product of which may be one of the many pathologies associated with human disease.